1. Field of the Invention
The present invention relates to a data reading and writing apparatus for connecting a portable recording medium (referred to as an IC card) to an external control unit so that the IC card can be controlled by the external control unit.
2. Description of the Prior Art
In an IC card, a semiconductor chip including a microcomputer and a memory unit (recording medium) are buried in a pocket-sized plastic card base. Further, 8 external terminals including a power supply terminal to the microcomputer and the memory unit are usually arranged on the surface of the card base.
In order to read or write information in or from the IC card, an IC card reading and writing apparatus is necessary. In one example of the prior art reading and writing apparatus, since no control circuit is incorporated in the apparatus, although the cost is low, there exists a problem in that when a high frequency clock signal is transmitted through a cable connected between the apparatus and an external control unit, signal crosstalk or reflection is produced in the cable, so that it is impossible to reliably control the IC card by the external control unit through a long cable connected between the two.
Here, crosstalk is a phenomenon such that when a high-frequency signal is passed through a first wire, a voltage is induced in a second wire arranged in parallel and adjacent to the first wire. Further, reflection means that since stray capacity and residual inductance exist in a wire, voltage vibration inevitably occurs between two active elements and a ringing voltage is reflected when no matching is made between two elements.
Further, in the other example of the prior art reading and writing apparatus, since a microprocessor is incorporated in the apparatus, although the problem involved in the first example apparatus can be solved, there exists another problem in that the cost is high and the external dimensions are relatively large.
The system configuration of the two typical examples of prior art IC card reading and writing apparatus will be described in further detail hereinafter with reference to the attached drawings under DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT.